Radio-frequency (RF) powered implantable stimulators and battery powered implantable stimulators are described in the art. See, for instance, U.S. Pat. No. 5,193,539 (“Implantable Microstimulator); U.S. Pat. No. 5,193,540 (“Structure and Method of Manufacture of an Implantable Microstimulator”); U.S. Pat. No. 5,312,439 (“Implantable Device Having an Electrolytic Storage Electrode”); U.S. Pat. No. 6,185,452 (“Battery-Powered Patient Implantable Device”); U.S. Pat. Nos. 6,164,284 and 6,208,894 (both titled “System of Implantable Device for Monitoring and/or Affecting Body Parameters”). Each of these patents is incorporated herein by reference in its respective entirety.
Implantable stimulators may be used to treat a variety of medical disorders. For example, to overcome sensorineural hearing loss, numerous cochlear implant systems, also referred to as implantable cochlear stimulator (ICS) systems, have been developed. These devices seek to bypass the hair cells in the cochlea, which are essential to hearing but which may not functioning properly, by presenting electrical stimulation directly to the auditory nerve fibers. This leads to the perception of sound in the brain and at least partial restoration of hearing function. To facilitate direct stimulation of the auditory nerve fibers, an array of electrodes may be implanted in the cochlea. A sound processor processes an incoming sound and translates it into electrical stimulation pulses applied by these electrodes to directly stimulate the auditory nerve.
A typical implantable stimulator is intended to remain permanently in the body of a patient once it is implanted. For this reason, many stimulation systems include one or more external devices configured to communicate with and support the stimulator or other device that is implanted within the patient. For example, some exemplary cochlear implant systems include a behind-the-ear (BTE) signal processor that may be positioned behind the ear and used to support an implanted stimulator.
The external portion of many stimulation systems includes a radio frequency (RF) power amplifier that is configured to provide power to the portion of the stimulation system that is implanted within the patient. The external portion will be specifically designed to meet the power requirements of the implanted device.